Change in coreboot[master]: drivers/analogix/anx7625: Fix edid_read()

[Yu-Ping Wu (Code Review)]

Attention is currently required from: Paul Menzel, Yu-Ping Wu.
Hello Hung-Te Lin, Wei-Shun Chang, build bot (Jenkins), Paul Menzel, Xin Ji,

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/coreboot/+/59540

to look at the new patch set (#3).

Change subject: drivers/analogix/anx7625: Fix edid_read()
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drivers/analogix/anx7625: Fix edid_read()

The current implementations of edid_read() and segments_edid_read() have
a few problems:

1. The type of variable `c` is incorrect, not matching the return type
   of sp_tx_aux_rd(). In addition, the meaning of `c` is unknown.
2. It is pointless to do `cnt++` when sp_tx_aux_rd() fails.
3. These two functions ignore the return value of
   anx7625_reg_block_read().
4. In segments_edid_read(), anx7625_reg_write() might return a positive
   value on failure.

Fix all of the 4 issues, and modify the code to be closer to kernel
5.10's implementation (drivers/gpu/drm/bridge/analogix/anx7625.c). Note
that, however, unlike in kernel, anx7625_reg_block_read() here doesn't
return the number of bytes. On success, 0 is returned instead.

In addition, following coreboot's convention, always return negative
error codes. In particular, change the return value to -1 for
edid_read() and segments_edid_read() on failure.

BUG=b:207055969
TEST=emerge-asurada coreboot
BRANCH=none

Change-Id: Ife9d7d97df2926b4581ba519a152c9efed8cd969
Signed-off-by: Yu-Ping Wu 
---
M src/drivers/analogix/anx7625/anx7625.c
1 file changed, 75 insertions(+), 67 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/40/59540/3